linux-kernel - Re: [PATCH 2/6] vsock: return errors other than -ENOMEM to socket

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Date:   Mon, 26 Sep 2022 15:21:45 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Bobby Eshleman <bobby.eshleman@...il.com>
Cc:     Bobby Eshleman <bobbyeshleman@...il.com>,
        Bobby Eshleman <bobby.eshleman@...edance.com>,
        Cong Wang <cong.wang@...edance.com>,
        Jiang Wang <jiang.wang@...edance.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org
Subject: Re: [PATCH 2/6] vsock: return errors other than -ENOMEM to socket

On Mon, Aug 15, 2022 at 10:56:05AM -0700, Bobby Eshleman wrote:
>This commit allows vsock implementations to return errors
>to the socket layer other than -ENOMEM. One immediate effect
>of this is that upon the sk_sndbuf threshold being reached -EAGAIN
>will be returned and userspace may throttle appropriately.
>
>Resultingly, a known issue with uperf is resolved[1].
>
>Additionally, to preserve legacy behavior for non-virtio
>implementations, hyperv/vmci force errors to be -ENOMEM so that behavior
>is unchanged.
>
>[1]: https://gitlab.com/vsock/vsock/-/issues/1
>
>Signed-off-by: Bobby Eshleman <bobby.eshleman@...edance.com>
>---
> include/linux/virtio_vsock.h            | 3 +++
> net/vmw_vsock/af_vsock.c                | 3 ++-
> net/vmw_vsock/hyperv_transport.c        | 2 +-
> net/vmw_vsock/virtio_transport_common.c | 3 ---
> net/vmw_vsock/vmci_transport.c          | 9 ++++++++-
> 5 files changed, 14 insertions(+), 6 deletions(-)
>
>diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>index 17ed01466875..9a37eddbb87a 100644
>--- a/include/linux/virtio_vsock.h
>+++ b/include/linux/virtio_vsock.h
>@@ -8,6 +8,9 @@
> #include <net/sock.h>
> #include <net/af_vsock.h>
>
>+/* Threshold for detecting small packets to copy */
>+#define GOOD_COPY_LEN  128
>+

This change seems unrelated.

Please move it in the patch where you need this.
Maybe it's better to add a prefix if we move it in an header file (e.g.  
VIRTIO_VSOCK_...).

Thanks,
Stefano

> enum virtio_vsock_metadata_flags {
> 	VIRTIO_VSOCK_METADATA_FLAGS_REPLY		= BIT(0),
> 	VIRTIO_VSOCK_METADATA_FLAGS_TAP_DELIVERED	= BIT(1),
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index e348b2d09eac..1893f8aafa48 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1844,8 +1844,9 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
> 			written = transport->stream_enqueue(vsk,
> 					msg, len - total_written);
> 		}
>+
> 		if (written < 0) {
>-			err = -ENOMEM;
>+			err = written;
> 			goto out_err;
> 		}
>
>diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
>index fd98229e3db3..e99aea571f6f 100644
>--- a/net/vmw_vsock/hyperv_transport.c
>+++ b/net/vmw_vsock/hyperv_transport.c
>@@ -687,7 +687,7 @@ static ssize_t hvs_stream_enqueue(struct vsock_sock *vsk, struct msghdr *msg,
> 	if (bytes_written)
> 		ret = bytes_written;
> 	kfree(send_buf);
>-	return ret;
>+	return ret < 0 ? -ENOMEM : ret;
> }
>
> static s64 hvs_stream_has_data(struct vsock_sock *vsk)
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 920578597bb9..d5780599fe93 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -23,9 +23,6 @@
> /* How long to wait for graceful shutdown of a connection */
> #define VSOCK_CLOSE_TIMEOUT (8 * HZ)
>
>-/* Threshold for detecting small packets to copy */
>-#define GOOD_COPY_LEN  128
>-
> static const struct virtio_transport *
> virtio_transport_get_ops(struct vsock_sock *vsk)
> {
>diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
>index b14f0ed7427b..c927a90dc859 100644
>--- a/net/vmw_vsock/vmci_transport.c
>+++ b/net/vmw_vsock/vmci_transport.c
>@@ -1838,7 +1838,14 @@ static ssize_t vmci_transport_stream_enqueue(
> 	struct msghdr *msg,
> 	size_t len)
> {
>-	return vmci_qpair_enquev(vmci_trans(vsk)->qpair, msg, len, 0);
>+	int err;
>+
>+	err = vmci_qpair_enquev(vmci_trans(vsk)->qpair, msg, len, 0);
>+
>+	if (err < 0)
>+		err = -ENOMEM;
>+
>+	return err;
> }
>
> static s64 vmci_transport_stream_has_data(struct vsock_sock *vsk)
>-- 
>2.35.1
>